Alex Mustard / Backlit detail of branching fire coral (Millepora alcicornis) showing the hair like polyps, filled with stinging nematocysts. East End, Grand Cayman, Cayman Islands. Caribbean Sea.

Solvin Zankl / Deepsea Siphonphore {Nectalia sp}, Atlantic ocean

Doug Perrine / Blue dragon / Blue seaslug (Glaucus atlanticus) feeding on a Portuguese man o' war (Physalia utriculus) along with a much smaller relative, Glaucilla sp. (upside down); Glaucus and Glaucilla store th...

Alex Mustard / Backlit photo of stinging nematocysts on colony of Fire coral (Millepora dichotoma) Gubal Island, Egypt. Strait Of Gubal, Red Sea.

Georgette Douwma / Fire coral (Millepora dichotoma) a hydroid, showing the hairs that are covered in cells called nematocysts, used mainly as a defense mechanism against fish which may feed upon it as well as against pr...

Georgette Douwma / Fire coral (Millepora dichotoma) a hydroid, showing the hairs that are covered in cells called nematocysts, used mainly as a defense mechanism against fish which may feed upon it as well as against pr...

Alex Mustard / Aeolid nudibranch (Flabellina pedata) feeding on its prey of hydroids. This species cannot only eat the stinging hydroids without getting stung, but the stinging nematocysts of the hydoid pass through...

Alex Mustard / Brain coral (Pseudodiploria strigosa) poylps capturing a planktonic worm, photographed under blue light to excite the fluorescence. The coral polyps glow green and the worm glows orange. The coral pol...

Pete Oxford / Fire Coral (Millepora alcicornis) with fine hairs that contain nematocysts which sting on contact, Belize Barrier Reef, Belize

Jeff Rotman / Stinging nematocysts on Fried egg jellyfish, Italy {Cotylorhiza tuberculata}